Reza,

ok, the chips you are using, could fail. BUT, I would rather focus on the PCB. How to detect faulty solder joints, halfway cut PCB tracks, and other nasty things?

I would do a temperature cycling test which encompasses the nominal temperature range plus a 10 deg margin.

How is the PCB mounted? Can any parts of it shake and bend? In case there are small vibrations around, you also could think about a small-scale vibration test.

Juergen